BigPinkLad - My fault, counting Wales as a separate kingdom.
The Union Flag, or Union Jack, is the national flag of the United Kingdom and it is so called because it embodies the emblems of the three countries united under one Sovereign - the kingdoms of England and Wales, of Scotland and of Ireland (although since 1921 only Northern Ireland has been part of the United Kingdom).
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The Welsh dragon does not appear on the Union Flag. This is because when the first Union Flag was created in 1606, the Principality of Wales by that time was already united with England and was no longer a separate principality.
http://www.royal.gov.uk/output/page398.asp

Beg your pardon
Wilfried